well vag probably didnt - but then they probably designed them uniformly enough to not need balancing, as clutches would be i dare say. But skimming some metal off the back of a flywheel might upset its original balance....
Not saying it would if done uniformly, but it might.
When a flywheel is lightened, it is machined uniformly. It's not a case of drilling holes like on a crank's counter balance weights. This reduces the likelyhood of upsetting the balance.
However, a decent machine shop with modern equipment will be able to machine and balance parts to closer tolerances than VW did at the factory during mass production.
Ideally you would have the flywheel balanced after it's been lightened, but then ideally you'd have the whole rotating mass dynamically balanced. All depends how far you want to go.
Yeah Dan, the full balance is crank pulley, crankshaft, flywheel and clutch cover. The clutch plate doesn't get balanced. Weight matching pistons and rods is going into blueprint territory, good but expensive due to the time it takes.
